1. Field of the Invention
This invention relates generally to a method and means for compacting and expanding stored information, sometimes referred to as memory space allocation, in a computer memory, and more particularly to a method of optimizing memory space in a control program which is changed while the control program is running to control a process uninterrupted.
2. Description of the Prior Art
Data processors or programmable controllers are known which store control programs for controlling equipments in various types of processes. For various reasons it is frequently desirable or necessary to modify these programs in order to implement changes to alter the manner in which a process is controlled.
To the best of the inventor's knowledge, there is no known method for modifying a control program in an on-line computer system while still running the control program such that the process is controlled uninterrupted and at the same time optimize the memory space of the modified control program. A need exists to be able to perform this type of program modification in that it is extremely costly to shut down a completely automated process control system to make program changes. Additionally, when memory space is not optimized, a great deal of memory space is wasted which could be made available for the retention of other programs or for storing data. Costs occur because of the stoppage in production and the possibility of having to pay idle workers while the program changes are being made. In view of these adversaties, it is highly desirable that a means and method be provided to prevent production stoppages while changing a control program whereby memory space is optimized concurrently with the changes.